Re: Regarding B-Tree Lookup

On 2 May 2017 7:34 pm, "Michael Paquier" <michael(dot)paquier(at)gmail(dot)com> wrote:

On Tue, May 2, 2017 at 6:12 PM, Mahi Gurram <teckymahi(at)gmail(dot)com> wrote:
> I'm building some custom extension on top of postgres 9.6.1. As part of
> that, I would like to read Heap Tuple directly from my extension using
> Primary Key.
>
> By default, postgres table index(B-Tree) its PrimaryKey(PK). So, i would
> like to get TID by doing a lookup into PK's B-Tree index. Using which i
> could read HeapTuple directly.

Use the heapam and indexam.

There's a handy wrapper for simpler queries in genam. See
systable_beginscsn etc. AFAIK these aren't really restricted to system
tables.

>
> Please suggest me the easiest way to lookup into PK's B-Tree index for
> getting TIDs.

Why don't you just use SPI within your extension? No need to copy the
logic for btree lookups this way.
https://www.postgresql.org/docs/9.6/static/spi.html

SPI is certainly the simplest way.

> Suggesting a postgres extensions which does B-Tree lookup will also helps
> me.

Pglogical has lots of direct heap and index access via genam.